JP2000116652A - Ultrasonic imaging method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the number of beams by reducing the clearance among a plurality of ultrasonic beams by generating an image on the basis of parametric echoes of ultrasonic waves sent when sending simultaneously ultrasonic beams in a plurality of azimuth in a subject and generating an image on the basis of the echoes. SOLUTION: When an ultrasonic probe 2 is butted against a desired part of a subject 4 and imaging is started by operating an operating section 20, multi beam sector scanning of eight sound rays for example, is performed, and harmonic echoes are generated due to the non-linearity of ultrasonic waves propagation in the subject 4. Higher harmonic echoes that are parametric echoes are extracted in a B mode processing section 10 having eight filter units in response to echo reception signals of eight sound rays, and B mode image signals are generated on the basis of the harmonic echoes. An image is formed on the basis of the harmonic echoes in an image processing section 14 and is displayed on a display section 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic imaging method and apparatus, and more particularly, to an ultrasonic imaging method that simultaneously transmits an ultrasonic beam in a plurality of directions in a subject and generates an image based on the echo. Method and apparatus.

[0002]

2. Description of the Related Art Ultrasound imaging in which an ultrasonic beam is simultaneously transmitted in a plurality of directions in a subject and an image is generated based on an echo of the ultrasonic beam is used for multi-beam imaging.
eam) It is called ultrasonic imaging. Multi-beam ultrasonic imaging is efficient because a single transmission and reception of ultrasonic waves can simultaneously acquire echo signals of a plurality of sound rays, so that the efficiency is high, and the imaging frame rate (framer) is high.
ate) is used for speeding up.

[0003] A plurality of ultrasonic beams are formed by corresponding beamformers. FIG. 8 shows a beam profile of an ultrasonic wave formed by the beam former.
An example of e) is shown. As shown in the figure, the beam profile includes a main lobe m generated in front of the azimuth (angle 0 °), side lobes s generated on both sides thereof, and pedestals generated on both sides thereof. pedestal) p. Due to the pedestal p, about -30 even at an angle of ± 20 °
It has a signal strength of dB.

[0004]

When a multi-beam is used, it is necessary to sufficiently separate the directions of the individual beams in order to avoid interference due to side lobes and pedestals.
For example, in the case of the beam profile of FIG.
If it is intended to be less than dB, the directions of the individual beams must be separated by at least 50 ° or more.

For this reason, for example, 64 channels (cha)
nnel) of ultrasonic transducer arrays (tran
When the sducer array is used, the number of practically usable multi-beams is about 2, and there is a problem that a sufficient number of multi-beams cannot always be obtained.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to realize an ultrasonic imaging method and apparatus capable of simultaneously transmitting and receiving a large number of multi-beams.

[0007]

Prior to describing the means for solving the problem, the nature of the parametric component of the ultrasonic wave will be described in advance. The waveform of the ultrasonic wave is distorted due to the non-linearity of the ultrasonic wave propagation in the subject, and second, third, or higher harmonics are generated based on the distortion. When two ultrasonic waves having different frequencies are transmitted at the same time, ultrasonic waves having the sum and difference frequencies of the frequencies are generated. Such ultrasound is referred to herein as a parametric component.

Due to the second-order or higher-order effects of nonlinearity, the distortion of the waveform is n (> 2) of the instantaneous sound pressure of the ultrasonic wave.
Since it is proportional to the power, the signal strength of the parametric component is proportional to the nth power of the instantaneous sound pressure of the transmitted ultrasonic wave.

For this reason, when attention is paid to, for example, a second-order parametric component, the beam profile is obtained by squaring the signal intensity of the beam profile of the fundamental wave. For example, as shown in FIG. It is greatly reduced and the directivity is improved. The present invention is based on this property of the parametric component of ultrasound,
Use that echo. In this document, a parametric echo is referred to as a parametric echo.
c echo).

(1) A first invention for solving the above problems is an ultrasonic imaging method for simultaneously transmitting ultrasonic beams in a plurality of directions in a subject and generating an image based on the echoes. Generating an image based on a parametric echo of the transmitted ultrasonic wave.

(2) A second invention for solving the above problems is an ultrasonic imaging apparatus which simultaneously transmits ultrasonic beams in a plurality of directions in a subject and generates an image based on the echoes. An ultrasonic imaging apparatus comprising: an image generating unit configured to generate an image based on a parametric echo of the transmitted ultrasonic wave.

In the first invention or the second invention, it is preferable that the parametric echo is a second harmonic echo in order to obtain a relatively high-level parametric echo.

(Operation) In the present invention, the directivity of the parametric component of the ultrasonic wave is used to reduce the distance between a plurality of ultrasonic beams and increase the number of multi-beams.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiment. FIG. 1 shows a block diagram of the ultrasonic imaging apparatus. This device is an example of an embodiment of the present invention. The configuration of the present apparatus shows an example of an embodiment relating to the apparatus of the present invention. An example of an embodiment of the method of the present invention is shown by the operation of the present apparatus.

The configuration of the present apparatus will be described. As shown in FIG. 1, the present apparatus has an ultrasonic probe (probe) 2. The ultrasonic probe 2 has an ultrasonic transducer array (not shown). The ultrasonic transducer array is configured by arranging a plurality of ultrasonic transducers in an appropriate array such as a one-dimensional array. Individual ultrasonic transducers are, for example, PZT (titanium (T
i) Lead zirconate (Zr)) ceramics (cera)
mics). The ultrasonic probe 2 is used in contact with the subject 4.

The ultrasonic probe 2 is connected to a transmitting / receiving unit 6. The transmission / reception unit 6 supplies a drive signal to the ultrasonic probe 2 to transmit ultrasonic waves. The transmitting / receiving unit 6 also receives the echo signal received by the ultrasonic probe 2.

FIG. 2 shows a block diagram of the transmitting / receiving section 6. As shown in FIG. As shown in the figure, the transmission / reception unit 6 transmits a signal at a transmission timing (tim).
ing) generating circuit 602. The transmission timing generation circuit 602 is connected to the transmission beamformer 604. The transmission timing generation circuit 602 periodically generates a transmission timing signal and inputs the signal to the transmission beamformer 604.

The transmission beamformer 604 is connected to a transmission / reception switching circuit 606. Transmission beamformer 604
Generates a transmission beamforming signal based on the transmission timing signal and inputs the signal to the transmission / reception switching circuit 606.

The transmission beamformer 604 is a multi-beamformer.
g), for example, eight beamforming units (beamforming unit) not shown.
t), thereby producing eight sets of drive signals, ie, eight sets of beamforming signals, for forming eight ultrasonic beams having different directions. Each set of beamforming signals is provided with a time difference corresponding to the azimuth and is composed of a plurality of drive signals.

The transmission / reception switching circuit 606 inputs eight sets of beam forming signals to the ultrasonic transducer array. In the ultrasonic transducer array, a plurality of ultrasonic transducers constituting a transmission aperture each generate an ultrasonic wave having a phase difference corresponding to a time difference of a drive signal. By the wavefront synthesis of the ultrasonic waves, an ultrasonic beam along eight sound rays having different directions, that is, a multibeam is formed.

In the present apparatus, as will be described later, an image is formed based on an echo (harmonic echo) based on a harmonic of the transmitted ultrasonic wave. The harmonic echo is an example of an embodiment of the parametric echo in the present invention.

As shown in FIG. 9, the beam profile of the harmonics of the transmitted ultrasonic wave has significantly reduced side lobes s and pedestal p, resulting in extremely good directivity, for example, a signal intensity of -40 dB. The angle of the beam narrows to about ± 10 ° from the front of the beam. Therefore, the separation angle between the beams in the multi-beam can be set small, and the number of the multi-beams can be set to, for example, eight.
Note that the number of multi-beams is not limited to eight.

The transmission / reception switching circuit 606 is connected to a reception beam former 610. The transmission / reception switching circuit 606 includes:
A plurality of echo signals received by the receiving aperture in the ultrasonic transducer array are input to the receiving beamformer 610. The receiving beam former 610 performs multi-beam forming of a receiving wave corresponding to a sound ray of a transmitting wave, and has, for example, eight beam forming units (not shown), thereby forming eight transmitting sound rays having different directions. Along with the received echo signal. Specifically, each beam forming unit adjusts the phase by giving a time difference to a plurality of received echoes, and then adds them to form an echo reception signal along the sound ray.

The transmission of the ultrasonic beam is repeatedly performed at predetermined time intervals by a transmission timing signal generated by the transmission timing generation circuit 602. In each case, the azimuths of the eight sound rays are simultaneously changed by a predetermined amount by the transmission beam former 604 and the reception beam former 610.
As a result, the inside of the subject 4 is sequentially scanned by sound rays of eight lines. The above-mentioned transmission timing generation circuit 602 to reception beam former 610 are controlled by the control unit 18 described later.

The transmission / reception section 6 having such a configuration performs, for example, scanning as shown in FIG. That is, a fan-shaped two-dimensional area 206 is scanned in the θ direction by eight sound rays 202 extending in the z direction from the radiation point 200, and a so-called sector scan (s
vector scan).

When the transmitting and receiving apertures are formed by using a part of the ultrasonic transducer array, the apertures are sequentially moved along the array to perform scanning as shown in FIG. 4, for example. Can be.
That is, the sound ray 202 emitted from the radiation point 200 in the z direction
Is translated along the linear trajectory 204, so that the rectangular two-dimensional area 206 is scanned in the x direction, and a so-called linear scan is performed.

The ultrasonic transducer array is
A so-called convex array (convex array) formed along an arc extending in the ultrasonic wave transmission direction.
In the case of y), the sound ray operation similar to the linear scan is performed, for example, as shown in FIG.
It is needless to say that so-called convex scanning can be performed by moving 00 along the arc-shaped trajectory 204 and scanning the fan-shaped two-dimensional area 206 in the θ direction.

The transmission / reception unit 6 is connected to a B-mode (mode) processing unit 10. The transmission / reception unit 6 inputs an echo reception signal of each multi-beam sound ray to the B-mode processing unit 10. The B-mode processing unit 10 forms a B-mode image signal based on the echo reception signal.

The B-mode processing unit 10 has a filter 102 as shown in FIG. The filters 102 correspond to eight filter units (not shown) corresponding to the echo reception signals of the eight sound rays.
it). Each filter unit extracts a harmonic echo, that is, an echo reception signal having the same frequency as the second harmonic (second harmonic) of the fundamental frequency of the transmitted ultrasonic wave, for example.

The filter may extract a third or higher harmonic as required. Higher harmonics are preferred in that they further improve the beam profile. However, the second harmonic echo is preferable because it has the highest signal level among the harmonic echoes. Hereinafter, an example of the second harmonic echo will be described, but the same applies to the third and higher harmonics.

The filter 102 is connected to a logarithmic amplifier 104. The logarithmic amplifier circuit 104 has eight logarithmic amplifier units corresponding to the eight filter units, and each logarithmically amplifies the second harmonic echo. The logarithmic amplifier circuit 104 is connected to the envelope detection circuit 106. The envelope detection circuit 106 has eight envelope detection units corresponding to the eight logarithmic amplification units, and each performs envelope detection of the logarithmically amplified second harmonic echo. As a result, a B-mode image signal representing the intensity of the second harmonic echo at each reflection point on the sound ray is obtained simultaneously for eight sound rays.

The B-mode processing unit 10 is connected to the image processing unit 14. The B-mode processing unit 10 inputs a B-mode image signal of eight sound rays to the image processing unit 14. Image processing unit 14
Is for generating a B-mode image based on a B-mode image signal input from the B-mode processing unit 10. Since the B-mode image signal is based on the second harmonic echo,
The B-mode image is a second harmonic echo image. The B-mode processing unit 10 and the image processing unit 14 are an example of an embodiment of an image generating unit according to the present invention.

As shown in FIG. 7, the image processing section 14 includes a sound ray data memory 142 connected by a bus 140 and a digital scan converter.
verter 144, an image memory 146, and an image processor 148.

The B-mode image signal input from the B-mode processing unit 10 for each sound ray is stored in the sound ray data memory 142 as a digital signal. Sound ray data memory 142
A sound ray data space is formed therein.

Digital Scan Converter 144
Converts data in the sound ray data space into data in the physical space by scan conversion. The image data converted by the digital scan converter 144 is stored in the image memory 1
46 is stored. The image memory 146 stores image data of a physical space. The image processor 148 performs predetermined data processing on the data in the sound ray data memory 142 and the image memory 146, respectively.

A display unit 16 is connected to the image processing unit 14. The display unit 16 receives an image signal from the image processing unit 14 and displays an image based on the image signal. Display 16
Is, for example, a graphic display.
display).

The transmission / reception section 6, B-mode processing section 10,
The image processing unit 14 and the display unit 16 are connected to the control unit 18. The control unit 18 supplies a control signal to each of these units to control the operation. In addition, various notification signals are input to the control unit 18 from each controlled unit. The operation of the present device proceeds under the control of the control unit 18.

An operation unit 20 is connected to the control unit 18. The operation unit 20 is used by an operator to input commands, information, and the like to the control unit 18. The operation unit 20 includes, for example, an operation panel (panel) including a keyboard and other operation tools.

The operation of the present apparatus will be described. The operator touches the ultrasonic probe 2 to a desired portion of the subject 4 and operates the operation unit 20 to perform imaging. The imaging is performed under the control of the control unit 18 based on a command or the like input from the operation unit 20.

As a result, a multi-beam sector scan with eight sound rays is performed as shown in FIG. 3, for example. Since the number of multi-beams is set to 8, scanning can be performed at a frame rate four times faster than the conventional example in which the number of multi-beams is two. Alternatively, a four times wider area can be scanned at the same frame rate. Of course, the same applies to the case where the linear scan and the convex scan shown in FIGS. 4 and 5 are performed.

In the subject 4, a second harmonic echo is generated due to the nonlinearity of the ultrasonic wave propagation. B-mode processing unit 10
Generates a B-mode image signal based on the second harmonic echo. These B-mode image signals are stored in the sound ray data memory 142 of the image processing unit 14. The image processor 148 scan-converts the B-mode image data in the sound ray data memory 142 with the digital scan converter 144 and writes the data in the image memory 146. Image memory 14
The image written in 6 is displayed on the display unit 16. As a result, a B-mode image based on the second harmonic echo is displayed as a visible image.

In the above, the parametric echo has been described as an example of a harmonic echo. However, the same effect can be obtained by using an echo having a sum or difference frequency in a two-frequency moving wave transmission.

Also, the ultrasonic transducer array has one
Although an example in which the array is a dimensional array has been described, the array is not limited to a one-dimensional array and may be an appropriate array such as a two-dimensional array. When a three-dimensional area of a subject is scanned using a two-dimensional array, the frame rate generally tends to be slow or the imaging area tends to be narrow. However, since the number of multi-beams is large, these can be greatly improved.

In addition to the array, an ultrasonic probe using a single ultrasonic transducer can improve the beam profile by using a parametric echo. Similar effects can be obtained when performing acoustic imaging.

Although the example of the B mode imaging has been described, the ultrasonic imaging is not limited to this, and the Doppler shift of the parametric echo is performed.
Needless to say, a dynamic image may be captured using ft).

[0046]

As described above in detail, according to the present invention, it is possible to realize an ultrasonic imaging method and apparatus capable of simultaneously transmitting and receiving a large number of multi-beams.

[Brief description of the drawings]

FIG. 1 is a block diagram of a device according to an example of an embodiment of the present invention.

FIG. 2 is a block diagram of a transmission / reception unit in the device shown in FIG.

FIG. 3 is a conceptual diagram of sound ray scanning by the device shown in FIG.

FIG. 4 is a conceptual diagram of sound ray scanning by the device shown in FIG.

FIG. 5 is a conceptual diagram of sound ray scanning by the device shown in FIG.

FIG. 6 is a block diagram of a B-mode processing unit in the device shown in FIG.

FIG. 7 is a block diagram of an image processing unit in the apparatus shown in FIG.

FIG. 8 is a diagram illustrating an example of a beam profile of a beam former.

FIG. 9 is a diagram illustrating an example of a beam profile of a beam former.

[Explanation of symbols]

 2 Ultrasonic probe 4 Subject 6 Transmission / reception unit 10 B-mode processing unit 14 Image processing unit 16 Display unit 18 Control unit 20 Operation unit 602 Transmission timing generation circuit 604 Transmission beam former 606 Transmission / reception switching circuit 610 Receiving beam former 102 Filter 104 Logarithmic amplification circuit 106 Envelope detection circuit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4C301 AA02 BB01 BB02 BB18 BB23 EE11 GB03 HH24 HH38 HH39 HH43 HH45 HH48 HH60 JB26 JB29 JB46 5B057 AA07 BA05 CC01 DA03 DC08 DC22

Claims (2)

[Claims] 1. An ultrasonic imaging method for simultaneously transmitting ultrasonic beams in a plurality of directions in a subject and generating an image based on the echoes, wherein the ultrasonic beam is transmitted based on a parametric echo of the transmitted ultrasonic waves. An ultrasonic imaging method, which generates an image. 2. An ultrasonic imaging apparatus for simultaneously transmitting ultrasonic beams in a plurality of directions in a subject and generating an image based on the echoes, based on a parametric echo of the transmitted ultrasonic waves. An ultrasonic imaging apparatus, comprising: an image generating unit that generates an image.